1. Field of the Invention:
This invention is directed to multifunctional lubricant additives and to compositions containing same. A more particular aspect of this invention is directed to metal salts of partially phosphosulfurized pentaerythritol and trimethylolpropane based hydroxyl-containing esters and to lubricating fluids containing said metal salts.
2. Discussion of Prior Art:
The metal surfaces of machinery or engines operating under heavy loads wherein metal slides against metal may undergo excessive wear or corrosion. Often, the lubricants used to protect the metal surfaces deteriorate under such heavy loads and as a result, do not prevent wear at the points of metal to metal contact. Consequently, the performance of the machine or engine will suffer, and in aggravated cases the machine or engine may become completely inoperative.
It is also known that lubricants are prone to oxidative deterioration when subjected to elevated temperatures or even when they are exposed to atmospheric conditions for long periods of time. Such deterioration of lubricants, including lubricating oils and greases, produces loss of lubricating properties of the oil, grease or other lubricant subjected to oxidation.
Accordingly, there is a need for a multifunctional additive system capable of effectively reducing wear, inhibiting corrosion and reducing oxidative deterioration. There have been many attempts to devise additive systems which would provide satisfactory protection in imparting friction reducing, antioxidant and anticorrosion properties to lubricants. Many prior art additives have, however, been only marginally effective in accomplishing such objective except at unacceptably high concentrations, especially when the lubricants are subjected to drastic oxidizing conditions.
U.S. Pat. No. 3,652,410 describes multifunctional lubricant additive compositions comprising overbased metal salts and sulfur-containing compounds. U.S. Pat. No. 3,150,157 describes borated monoacylated trimethylolalkanes as motor fuel additives. However, no known art discloses or suggests the use of metal salts of pentaerythritol or trimethylolpropane based hydroxyl-containing esters as multifunctional lubricant additives.